This invention relates to a manually propelled cycle, such as a bicycle, having pedal levers that pivot about a pivot axis to permit the pedal levers to move in a reciprocal fashion to propel the cycle as the user reciprocates the pedal levers up and down. More particularly, this invention relates to a cycle in which the pivot axis is shiftable to selectively vary the transmission ratio of the cycle.
Various types of manually propelled cycles are known such as bicycles and tricycles. A typical bicycle includes a frame, a front wheel and a rear wheel rotatably carried on the frame, a seat for the operator, a steering handle to steer the bicycle, and rotary pedals for propelling the bicycle. The pedals are part of a rotary crank mechanism that is connected by a chain and sprocket drive to the hub of the rear wheel. The sprocket drive is adjustable for varying the sprocket ratio to vary the speed of the bicycle for a given amount of effort by the operator by varying the transmission ratio. Tricycles are similar but have a pair of rear wheels instead of a single rear wheel.
Some bicycles are known which use reciprocal pedal levers instead of pedals on a rotary crank. In these cycles, each pedal lever is pivotally connected to the bicycle frame with the pedal lever having a foot operated pedal carried on one end. The other end of the pedal lever is connected by flexible motion transmitting members to one of the wheels of the bicycle, typically to the rear wheel, so that up and down reciprocal motion of each pedal lever is converted into rotary motion of the wheel. The operator sits on the seat and propels the bicycle by reciprocating the pedal carrying ends of the pedal levers up and down.
U.S. Pat. No. 3,888,512 to Peterson, U.S. Pat. No. 3,954,282 to Hege, U.S. Pat. No. 4,300,784 to Efros, U.S. Pat. No. 5,335,927 to Islas, and U.S. Pat. No. 5,785,337 to Ming all disclose bicycles of the reciprocal pedal lever type. Many people consider such bicycles easier to ride than bicycles having pedals carried on rotary cranks. This is thought to be due to the up and down motion of the legs that is required to reciprocate the pedal levers up and down. This up and down leg motion is easier and more comfortable for many people than having to rotate the leg and foot in a complete circle. There is less motion involved and less stress on the user""s joints in accomplishing reciprocal pedal action than complete circular rotation of the pedals.
One difficulty with bicycles having reciprocal pedal levers is the ability to change the transmission ratio. In a bicycle having a conventional rotary crank, the hub of the rear wheel often has a plurality of transmission ratio change sprockets. The transmission ratio change is accomplished by shifting the chain from one sprocket to the next to change the transmission ratio. The use of hubs with multiple transmission ratio change sprockets and the derailleurs for moving the chain between the sprockets is well developed in rotary crank bicycles.
However, for bicycles with reciprocal pedal levers, the mechanisms for changing the transmission ratio are much less well developed. The Efros patent referenced above teaches a system of changing transmission ratio by changing the location of where the force transmitting member connects to the pedal lever. The Peterson patent referenced above teaches shifting the pivot axis about which the pedal levers pivot. However, both of these approaches have been executed in fairly complicated and expensive ways. A need exists in the art for a cycle with reciprocal pedal levers that has a simple, durable and reliable mechanism for changing the transmission ratio of the cycle.
One aspect of this invention relates to a manually propelled cycle. The cycle comprises a frame which is supported for rolling over the ground by a front wheel and at least one rear wheel. Both wheels are rotatably carried on the frame. A seat is provided on the frame to accommodate a seated operator. A steering handle is provided on the frame to steer the frame. Reciprocal pedal levers are connected to the frame for pivoting about a pivot axis. Each pedal lever is connected to a motion transmitting member for transmitting reciprocal motion of the pedal lever to a hub of one of the wheels on the frame for propelling the frame. The frame and the pedal levers each have at least one rack affixed thereto. The pivot axis of the pedal levers is formed by a pinion engaged with the racks on the frame and the pedal levers. A plurality of bearings are received around the pinion with at least one bearing extending between the pinion and the frame and at least one bearing extending between the pinion and each of the pedal levers.